Method for making a through opening in a high-pressure fuel reservoir, and apparatus for performing the method

ABSTRACT

A method for making a through opening in a high-pressure fuel reservoir that has an elongated, tubular jacket body, which body is provided in the longitudinal direction with a continuous recess, open on at least one side, that forms the interior of the high-pressure fuel reservoir, and the through opening is made in the jacket body in the form of a bore by a machining tool in such a way that this opening discharges into the continuous recess, in order to make it possible to produce bores without burrs, it is proposed that before the through opening is made, a pressure part is pressed against the inner wall of the jacket body in the region of the expected outlet of the through opening, and with the machine tool, drilling is done through the jacket body some distance into the pressure part.

PRIOR ART

[0001] The invention relates to a method and an apparatus for makingthrough openings in a high-pressure fuel reservoir.

[0002] From German Patent Disclosure DE 196 40 480 A1, a high-pressurefuel reservoir for a fuel injection system for internal combustionengines is known which comprises an elongated, tubular jacket body ofsteel into which a high-pressure fuel pump can be connected. The jacketbody has a longitudinally extending continuous recess, open on at leastone side, that forms the interior of the high-pressure fuel reservoir.In the fully installed state of the high-pressure fuel reservoir, the atleast one open end is closed by the attachment of the high-pressure fuelpump or of a pressure limiting valve, or in some other way. By way of aplurality of connections embodied on the jacket body and high-pressurelines connected to them, the fuel subjected to high pressure that iscontained in the high-pressure fuel reservoir is delivered toelectrically controlled injection valves, so-called injectors, forinjection into the combustion chambers of a self-igniting internalcombustion engine. A high-pressure fuel reservoir of this kind is alsoknown as a common rail. The connections of the high-pressure fuelreservoir are embodied in the form of connection stubs, which protrudefrom the jacket body and are each provided with a through openingembodied as a bore, which discharges into the continuous recess of thejacket body. The through openings can also discharge eccentrically intothe continuous recess.

[0003] In the conventional production of the through openings with amachining tool, a more or less markedly pronounced burr surrounding thebore is created at the outlet point of the tool in the continuousrecess. Because of the high internal pressure in the high-pressure fuelreservoir, which is about 1350 bar, and because of the narrow diametersof the bores, typically 2.4 mm, abrasive particles in the fuel causewear in the region of the encompassing edge formed by the throughopening and the inner wall of the continuous recess. The occurrence ofabrasive particles is disadvantageously further reinforced by the burrsurrounding the bore, because relatively large particles can becomedetached there and damage the injection nozzles. Furthermore, thepresence of a burr surrounding the bore favors the development of eddiesand unfavorable flow properties, which can very adversely affect theservice life of the high-pressure fuel reservoir, given the increasingpressure loads on it.

ADVANTAGES OF THE INVENTION

[0004] These disadvantages are reliably avoided by the method for makingthrough openings in a high-pressure fuel reservoir as defined by thecharacteristics of claim 1. Because before the through opening is made,a pressure part is pressed against the inner wall of the jacket body inthe region of the expected outlet of the through opening, and with themachine tool, drilling is done through the jacket body some distanceinto the pressure part, the occurrence of a burr surrounding the bore isadvantageously avoided. This method is especially advantageous at placesin the high-pressure fuel reservoir where later metal-cutting deburringis not possible.

[0005] It is also especially advantageous that because of the creationof the burr-free bores, a subsequent rounding off or chamfering of theedge formed by the bore and the inner wall of the continuous recess ismade possible, so that especially evenly rounded-off or chamfered edgestructures can be created. In the prior art, because of the developmentof a burr in the drilling, these methods do not lead to the desiredresults.

[0006] In the other claims, advantageous apparatuses for performing themethod are described.

[0007] Advantageously, to produce a through opening, a chucking devicethat can be introduced into the continuous recess can be used, having afirst chucking jaw, an interchangeable pressure part, a second chuckingjaw, and a chucking part disposed between the first chucking jaw and thesecond chucking jaw, by which chucking part the pressure part and thesecond chucking jaw can be pressed into contact with the inner wall ofthe continuous recess. Once the bore has been made, which ends in thepressure part in a blind bore, the chucking device is removed from thehigh-pressure fuel reservoir, and the pressure part is replaced. Thechucking device is now ready for use again. Advantageously, the pressurepart can be used as an insertion part inserted into a recess of thefirst chucking jaw. The pressure part comprises metal or a very hardplastic, which is approximately equivalent in its hardness to thehardness of the jacket body.

[0008] Advantageously, the radius of curvature of the face of thepressure part oriented toward the inner wall of the continuous' recessis adapted precisely, at the point intended for making the throughopening, to the radius of curvature of the inner wall of the continuousrecess.

[0009] An apparatus for rounding off the encompassing edge formed by thethrough opening and the inner wall of the continuous recess, whichincludes both a laser beam shining axially into the applicable bore anddisplaceable perpendicular to the axis of the bore and a rotatingdeflection mirror inclined relative to the laser beam, which mirror ismounted on a slide that is provided with an annular gear and can beintroduced into the continuous recess, is also advantageous.

[0010] For chamfering the encompassing edge formed by the throughopening and the inner wall of the continuous recess, a grinding devicewith a conical grinding head that can be introduced into the continuousrecess is also advantageous. Advantageously, the grinding device isdisposed on a rod. The motion of the grinding head in the continuousrecess is controllable in such a way, by a drive unit acting on the rod,that the grinding head is moved along the edge contour in accordancewith a preset program. Dimensional tolerances in the edge contour can becompensated for by a spring bearing of the grinding head.

DRAWINGS

[0011] One exemplary embodiment of the invention is shown in thedrawings and explained in the ensuing description.

[0012] Shown are

[0013]FIG. 1, a cross section through a high-pressure fuel reservoirwith a connection stub and an introduced chucking device, before a borefor the through opening is made;

[0014]FIG. 2, a cross section through the high-pressure fuel reservoirof FIG. 1, after the bore has been made;

[0015]FIG. 3, an apparatus with a laser for rounding off an edge formedby a bore and the inner wall of the continuous recess;

[0016]FIG. 4, an apparatus for chamfering an edge formed by a bore andthe inner wall of the continuous recess.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

[0017] In FIG. 1, a cross section is shown through a high-pressure fuelreservoir, which includes an elongated tubular metal jacket body 1,which for the sake of supplying fuel injection valves has formed-onconnection stubs 3 produced for instance by forging. Naturally stillother connection stubs 3 can also be provided, which serve to attach ahigh-pressure fuel pump or a pressure sensor. The interior of thehigh-pressure fuel reservoir is formed by a continuous recess 2,extending longitudinally of the jacket body 1 and preferably having acircular cross section. However, the cross section can take some otherform instead, and for instance can be elliptical. The continuous recess4 made in the jacket body 1 can be solidly closed on one face end. Theother face end is open and can for instance be closed by a screwed-onpressure limiting valve, the attachment of the high-pressure fuel pump,a lid, or in some other way.

[0018] As is also shown in FIG. 1, a chucking device is thrust into thecontinuous recess 2 from the open side of the high-pressure fuelreservoir. The chucking device includes a central chucking part 12 andtwo chucking jaws 10 and 11 of semicircular cross section. The chuckingjaws can have some other cross-sectional shape instead, however. In theexample shown here, the outside radius of the first chucking jaw 11 isadapted to the radius of curvature of the inner wall 4 of the continuousrecess 2. The outside radius of the second chucking jaw 10 is designedto be somewhat less than the radius of curvature of the inner wall 4 ofthe continuous recess 2. As can also be seen, the region of the secondchucking jaw 10 that is oriented toward the connection stub 3 isprovided with a recess 6, into which a pressure part 13 is inserted. Theface contour 14 of the pressure part 13 oriented toward the inner wall 4is adapted precisely to the contour of the inner wall 4. In theexemplary embodiment shown here, the face contour 14 and the inner wall4 accordingly have the same spherical radius of curvature. Otherrecesses and other pressure parts are correspondingly If provided on theother connection stubs of the jacket body 1. If not all the connectionstubs protrude in the same direction from the jacket body 1, then thechucking device may need to be rotated in order to produce all thebores. The chucking jaws 10, 11, the chucking part 12 and the pressureparts 13 are made from metal. However, it is also conceivable to usesome other suitable material. For instance, the pressure parts can alsobe made from a very hard plastic.

[0019] The central chucking part 12 also has a wedge-shaped contour. Byinsertion of the chucking part 12, the first chucking jaw 11 and thepressure part 13 are pressed against diametrically opposed portions ofthe inner wall 4 of the continuous recess. As is shown in FIG. 2, toproduce a through opening, a blind-borelike bore 5 is made, adjacent toa through opening, in the connection stub 3 and the pressure part 13.Drilling is done to some distance into the pressure part 13 from outsidethrough the connection stub 3 and the jacket body 1, using the drillingtool. Advantageously, drilling is done in such a way that the entire tipof the drilling tool enters into the pressure part 13. By means of thepressure part 13, the creation of a burr at the edge formed by the innerwall 4 and the bore 5 is avoided. The same procedure is employed for theother connection stubs. Then the drilling tool and the chucking device10, 11, 12, 13 are removed. The connection stubs 3 can now be providedwith a screw thread as well, onto which a high-pressure connecting linecan be connected via a cone seal. After the chucking device has beenremoved, the insertion parts 13 can be replaced. Now the chucking deviceis once again ready for making further bores in the next high-pressurefuel reservoir to be machined.

[0020] The encompassing edge 7 formed by the bores 5 and the continuousrecess 2 can also be rounded off, as is shown for a first exemplaryembodiment in FIG. 3. For this purpose, a laser beam 20 is used. A slide21 provided with a mirror 22 is introduced into the continuous recess 2.The slide has a countersunk feature 28, in which the mirror 22 isdisposed. The mirror 22 is supported rotatably about the axis of thelaser beam 20 via an annular gear 25, disposed in a recess 27 of theslide 21 and embodied here in the form of bevel gearing. A drive shaft26 disposed in the slide 21 drives the annular gear, causing the mirror22 to rotate about the axis of the laser beam 20. The mirror 22 isinclined by a variable angle relative to the axis of the laser beam 20,and this angle of inclination is adjusted via an adjusting mechanism.The laser beam 20 can be displaced perpendicular to the axis of the bore5, or perpendicular to the direction in which it is shone. This isrepresented by the arrow a in FIG. 3. As a result, the laser beamreflected from the mirror 22 migrates over the edge 7 at the positiondetermined by the rotary position of the mirror 22 and melts this edgeand thus rounds it off. The entire encompassing edge can thus be roundedoff by rotating the mirror and displacing the laser beam. By a suitablechoice of the rotary speed of the mirror 22 and the frequency with whichthe laser beam 20 is displaced perpendicular to the axis of the bore, itis also possible to machine regions of the edge 7 that are locatedoutside a radial plane. If the mirror 22 becomes fogged during themachining of the edge 7, it can be replaced.

[0021] Another exemplary embodiment for machining the edge 7 formed bythe bore 5 and the inner wall 4 of the continuous recess 2 is shown inFIG. 4. In this example, a grinding device 30 is used. The grindingdevice includes a turbo grinder with a conical grinding head 31; thishead is supported spring-elastically on the grinding device 30 via a pin32 and a spring 34 in such a way that the grinding head 31 can bedisplaced parallel to the pin 32, counter to the tensing force of thespring 34. A rod 33 serves to introduce the grinding device into thecontinuous recess 2. The grinding head 31 is placed with slight pressureagainst the edge 7. Via the rod 33, the motion of the grinding head 31in the continuous recess 2 is controlled, and the motion of the rod 33can be controlled for instance by a drive unit which is driven by anelectric motor and which moves the grinding head 31 along the edgecontour 7 in accordance with a preset program. Tolerances in the edgecontour 7 are compensated for by the spring bearing of the grinding head31. The encompassing edge 7 is chamfered in this way, and by means of asuitable course of motion it is possible here as well to machine regionsof the edge 7 that are located outside a middle radial plane. To thatend, in a first phase of motion, the grinding head 31 is first movedlongitudinally along the arrow c in FIG. 4 and at the same time isrotated toward the left, in the direction of the arrow d, about thecenter axis of the rod 33, and then in a second phase of motion, it ismoved onward in the direction of the arrow c in the longitudinaldirection and toward the right counter to the arrow d. In the thirdphase, the grinding head is moved backward counter to the arrow c andtoward the right again counter to the arrow d, and then in the fourthphase, it is moved onward longitudinally counter to the arrow c and atthe same time toward the left in the direction of the arrow d, so thatfinally it reaches the starting point on the edge contour 7 again.

[0022] Triggering the grinding head 31 can be facilitated still furtherif an axially movable stop 35 is introduced into the bore, against whichstop the tip of the conical grinding head 31 is pressed lightly.

[0023] The above-described method steps for producing the bore and forrounding off or chamfering the edge 7 can also be performed whenever thebore 5 discharges into the continuous recess 2 eccentrically to the axisthereof.

1. A method for making a through opening in a high-pressure fuelreservoir that has an elongated, tubular jacket body (1), which body isprovided in the longitudinal direction with a continuous recess (2),open on at least one side, that forms the interior of the high-pressurefuel reservoir, and the through opening (5) is made in the jacket body(1) in the form of a bore by a machining tool in such a way that thisopening discharges into the continuous recess (2), characterized in thatbefore the through opening is made, a pressure part (13) is pressedagainst the inner wall (4) of the jacket body (1) in the region of theexpected outlet of the through opening (5), and with the machine tool,drilling is done through the jacket body (1) some distance into thepressure part (13).
 2. The method of claim 1, characterized in thatafter the through opening (5) has been made, the encompassing edge (7)formed by the through opening (5) and the inner wall (4) of thecontinuous recess (2) is rounded off or chamfered.
 3. An apparatus forperforming the method of claim 1, characterized in that a chuckingdevice (10, 11, 12, 13) that can be introduced into the continuousrecess (2) can be introduced into the continuous recess (2) by a firstchucking jaw (10) having an interchangeable pressure part (13) and asecond chucking jaw (11) and a chucking part (12) disposed between thefirst chucking jaw (10) and the second chucking jaw (11), by whichchucking part the pressure part (13) and the second chucking jaw (11)can be pressed into contact with the inner wall (4) of the continuousrecess (2).
 4. The apparatus of claim 3, characterized in that thepressure part (13) can be used as an insertion part into a recess (6) ofthe first chucking jaw (10).
 5. The apparatus of claim 3 or 4,characterized in that the pressure part (13) comprises metal or a veryhard plastic.
 6. The apparatus of one of claims 3-5, characterized inthat the radius of curvature of the face (14) of the pressure part (13)oriented toward the inner wall (4) of the continuous recess (2) isadapted precisely, at the point intended for making the through opening(5), to the radius of curvature of the inner wall (4) of the continuousrecess (2).
 7. An apparatus for performing the method of claim 2,characterized in that for rounding off the encompassing edge (7) formedby the through opening (5) and the inner wall (4) of the continuousrecess (2), a laser beam (20) that shines axially into the applicablebore and is displaceable perpendicular to the axis of the bore and arotating deflection mirror (22) inclined relative to the laser beam (20)are provided, the mirror being mounted on a slide (21) that is providedwith an annular gear (25) and can be introduced into the continuousrecess (2).
 8. The apparatus for performing the method of claim 2,characterized in that for chamfering the encompassing edge (7) formed bythe through opening (5) and the inner wall (4) of the continuous recess(2), a grinding device (30), having a conical grinding head (31), thatcan be introduced into the continuous recess is provided.
 9. Theapparatus for performing the method of claim 8, characterized in thatthe grinding device (30) is disposed on a rod (33), and that the motionof the grinding head (31) in the continuous recess (2) is controllablein such a way, by a drive unit acting on the rod (33), that the grindinghead (31) is moved along the edge contour (7) in accordance with apreset program.
 10. The apparatus for performing the method of claim 9,characterized in that the grinding head (31) protrudes from the grindingdevice (30) approximately perpendicular to the rod (33) and is supportedaxially movably on the grinding device counter to the tensing force of aspring (34).